The present invention relates to a method for producing thin metal films by thermal vapor-deposition.
Thin metal films, typically having a thickness of 10 nm to about 10 .mu.m, can be economically produced through thermal vapordeposition (or evaporation, vacuum metallization). This method is utilized, for example, in the microelectronics area, wherein the metal contacts on the semiconductor components are constructed from one or more metal films that are deposited on top of one another.
During the deposition of such metal films, an inner mechanical stress (intrinsic stress) occurs. This inner mechanical stress limits the selection of the metals that can be utilized and the maximum thickness of the metal layer. The mechanical stress that occurs in the metal film, in particular, has the following disadvantages: it can cause the substrate to arc or sag; it can cause the adhesion of the metal film on the semiconductor surface to be deteriorated; and the electrical properties of the component can thereby be changed.
This mechanical stress can be either a compressive stress or a tensile stress. Typically, the method utilized to attempt to control the mechanical stresses is through the mutual compensation of layers having alternating compressive stress and tensile stress. G.E. Henlein and W.R. Wagner, J. Appl. Phys. 54, 6395 (1983) describes such a compensation method in a titanium-platinum layer format. The layer thicknesses are adapted, to one another, such that the inner tensile stresses of the titanium layer are compensated for by the inner compressive stresses of the platinum layer.
In a method referred to as deposition by sputtering, the stresses on the metal layer to be applied, are controlled by the pressure of the plasma, generally argon. However, this cannot be utilized in the thermal vapor-deposition (for vacuum metallization) of the metal film.